1. Field of the Invention
The present invention relates to a power combiner/distributor used in a microwave band, and a transmitter using the power combiner/distributor, and more particularly, to a countermeasure to reduce a distribution loss or a combination loss.
2. Description of the Related Art
The power combiner/distributor has been widely used for combining or distributing power. In the case where the power is distributed and input to a plurality of amplifiers that operate in parallel, or in the case where the powers from the amplifiers are combined together, when a part of the amplifiers that operate in parallel fail, impedances at input/output terminals of the failed amplifier change. As a result, the distribution loss or the combination loss occurs in the power combiner/distributor.
There is a method in which the power combiner/distributor is configured by a directional coupler in order to reduce such distribution loss or combination loss (for example, Japanese Patent Application Laid-open No. 2007-150377). In the power combiner/distributor thus configured, the failed amplifier is removed, and a terminal of the power combiner/distributor from which the amplifier has been removed is short-circuited or opened. As a result, because reflected power of the opened terminal is input to a termination resistor of the directional coupler, no impedance mismatching occurs, and the combination loss or the distribution loss can be reduced.
However, the related art suffers from the following problem.
In the conventional power combiner/distributor, the combination loss and the distribution loss are not caused by the impedance mismatching. However, power absorbed by the termination resistor of the directional coupler connected to the terminal from which the failed amplifier has been removed is lost. That is, the conventional power combiner/distributor suffers from such a problem that the power absorbed by at least the termination resistor is lost.